Method of separating hydrogen isotopes



United States Patent METHOD OF SEPARATING HYDROGEN ISOTOPES Oliver N. Salmon, Schenectady, N. Y., assignor to the No Drawing. Application October 17, 1956 Serial No. 616,581

1 Claim. c1. ms-114.2

This invention deals with a method of separating isotopes of hydrogen, and in particular with a method based on sorption.

It is an object of this invention to provide a method by which a mixture of hydrogen isotopes may be separated in a simple and eificient manner.

It has been found that, when finely divided palladium is contacted with a mixture of the hydrogen isotopes, the hydrogen is preferentially taken up by the palladium while the deuterium and tritium are sorbed to a lesser degree, the sorption of the tritium being least. Likewise, the rate of sorption of hydrogen, deuterium and tritium decreases in the order mentioned. The method of this invention utilizes these facts, and fractionation of hydrogen isotope mixtures is carried out by passing these mixtures over palladium; the result is a hydrogenenriched gas fraction held by the palladium and a remaining gas fraction enriched in deuterium and/or tritium.

The process can be carried out in an especially efiicient manner by using a number of palladium beds connected in series, thereby dividing the gas mixture in a Patented Dec. 9, 1958 ice palladium, or it may be pumped through the palladium by mechanical means. Another way of efiecting gas flow is by arranging a bed of uranium at the end of the line of the palladium'beds; the uranium acts as a chemical pump by pulling the gas through the palladium.

Instead of separating the various isotopes by fractional sorption, it is also feasible first completely to take up the entire mixture with palladium and then fractionally to evolve the gas mixture by gradually elevating the temperature and collecting the evolved gas in separate fractions; The tritium is evolved faster than the deuterium, and the deuterium faster than the hydrogen; thus tritium-enriched fractions are obtained first in this caseand hydrogen-enriched fractions last.

In the following an example is given to illustrate the process of the invention on a hydrogen-deuterium mixture.

EXAMPLE I A hydrogen-deuterium mixture, the quantity as well as: the composition of which had been determined, was: passed through two interconnected palladium beds in sue-- cession, each of which had a diameter of 1 inch and a height of 6 inches; each bed contained 35 grams of pal ladium black dispersed in 175 grams of silica sand of to 150 mesh. A uranium bed containing 33 grams of uranium was connected with the second palladium bed as a chemical pump. During sorption all three beds were at room temperature. After the entire gas quantity had been passed through the three beds, they were disconnected from each other, and each was heated separately to evolve the sorbed gas. A sample of the fraction from each bed was analyzed. Five runs were carried out with mixtures of diiferent hydrogen-deuterium ratios. The results of these experiments are given in the table below.

Summary of hydrogen isotope separation runs Original Compo- Pd Bed No. 1, Pd Bed No. 2, U Bed, Percent Run sition, Percent Percent Percent Sorption No. Time,

minutes H: D: Hz D2 H2 D2 H2 D2 260 cc. (STP) 58.5% of gas 20.5% of gas 15.8% of gas 2 89.85 I 10.15 94.7 I 91.7 I 8.25 78.3 21 7 5 259 cc. (STP) 48.8% of gas 23.8% of gas 23% of gas 3 48.6 I 51.4 67.1[ 329 59.8[ 40.2 297] 703 5 259 cc. fiSIP) 30% of gas 22% of gas 39% of gas 4 10.2 89.8 25. 1 I 74.9 20.4 I 79.6 6. 4 93.6 7

259 cc. (STP) 12 8% of gas 12.3% of gas 64.2% of gas 5 6.6 93.4 .2] 85. 14.5[ 85.6 3.9I 7

""" 261 cc. (STP) 15.8% of gas 22% of gas of gas corresponding number of fractions. For instance, in the case of a mixture of the three isotopes and the use of two palladium beds, the first palladium bed contains a hydrogen-enriched fraction, the second bed a deuteriumenriched fraction, and the escaping gas represents a tritium-enriched fraction. The various fractions may then be desorbed from the palladium and subjected to another fractionating cycle whereby further enrichment and separation are achieved. By using some of the beds for the sorption process while others are regenerated, for instance by heating, a semi-continuous operation is possible.

Palladium is preferably used in very finely divided form, for instance as palladium black or palladium sponge. It is advantageous to dilute the palladium by dispersing it in silica sand or other inert materials. The temperature of operation may vary widely; room temperature, approximately 25 C., has been found satisfactory. The gas mixture 'may either be brought to superatmospheric pressure prior to passing it over the EXAMPLE II This experiment was carried out using one palladium bed only, which had the same dimensions and contained the same quantity and kind of palladium-silica mixture as those used in Example I and 37 cc. (STP) of a hydrogen-tritium mixture containing 2.5% by volume of tritium. The entire gas mixture was adsorbed on the palladium at room temperature and 103 mm. Hg. Thereafter the palladium was heated slowly to about C,

and the bed was connected with a Toepler pump whereby the gas was sucked ofi.

The released gas was collected in two fractions, a .fi t qn of 1 m n a vs q ml i ast 9f 20-7 Iq .Ea h r t p wa a a y bvma s s sl tu swpy It will be understood that this.invention is not to be limited to the details given herein but that it may be modified within the scope of the appended claim.

What is claimed is: V

A process of separating a gaseous mixture of hydrogen and tritium, comprising contacting finely divided palladium with said mixture whereby the gaseous mixture is taken up'by 'sorption; gradually heating the palladium whereby a fraction rich' in'tritium is first given 01? and collecting the evolved fractions as' they are :formed.

References Cited in the file of this patent ia Naturwpl- 135 (19 12 gic3t18. Mellor: Comprehensive Treatise of Inorganic and Theoretical Chemistry, vol. 15, pages 616-624, Longmans, Green & 00., London (1936)." 

